Simplified reliability analysis of punching in reinforced concrete flat slab buildings under accidental actions

Abstract

Flat slab concrete buildings are widely found in infrastructure such as office and residential buildings or industrial facilities. The susceptibility of progressive collapse of such structures due to accidental loads is highly dependent on the structural performance of the slab-column connections. This paper presents a framework for a simplified reliability analysis and derivation of safety factors for computing the probability of punching of flat slab concrete buildings subjected to accidental loads such as column removal, slab falling from above or blast load. The main advantage of the proposed approach is that it considers in a simple manner, the uncertainty in the gravity load applied in the slab before the accidental event, which affects the inertial effects and demand/capacity ratio in the slab-column connections. Eurocode 2 and the Critical Shear Crack Theory for punching are used and extended to dynamic cases for the assessment of the demand/capacity ratio using computer-based time history finite element simulations. The proposed reliability method is applied to a case study of an existing building showing that the column removal situation is not always critical whereas the slab falling from above is much more detrimental

Effects of sudden failure of shoring elements in concrete building structures under construction

“…The building had three floors with RC flat-slabs 300 mm thick, 3.5 m between floors and columns 400 mm square which were irregularly distributed in plan. A more exhaustive description of the building, which was also the subject of other studies, can be found in Olmati et al [16]. Fig.…”

“…3. The FE model of the RC structure had been previously validated by Olmati et al [16] in a separate study on punching shear in slab/column joints due to accidental events. This FE model provided similar results of bending moments and deflections to that reported in CS report [28] for an elastic analysis with a quasi-static load combination used in design.…”

“…Belytschko-Schwer resultant beam elements [36] were used for the columns, stiffly connected to slabs and fully fixed in the foundations. The defined finite elements considered cracking and crushing, as well as yielding, hardening, softening, stiffness degradation due to cyclic loads and fracture of the reinforcement steel as specified in Eurocode 2 [16,25]. Further details of the simulation can be found in Olmati et al [16].…”

“…The numerical analyses of a RC building structure carried out in this work provide unique and novel evidence on the structural consequences of the structure-shoring system after the local failure of different shoring elements using the concept of notional member removal. This approach is commonly used for robustness analysis of permanent structures in research [16][17][18][19][20][21][22][23][24] and international codes [25][26][27]. This approach is based on the "sudden" removal of an element (scenario independent approach) to assess the capacity of the structure to redistribute the loads (alternative load path method) and to assess dynamic effects.…”

Análise mecânica e probabilística de estruturas treliçadas sujeitas ao colapso progressivo

“…Análises não lineares dinâmicas com a consideração de efeitos de amortecimento e taxa de carregamento são tratados por Olmati et al [179]. Wang et al [180] usaram modelos em multi-escala para investigar o desempenho das ligações viga/pilar por meio de análise não linear estática e dinâmica.…”